grgsm_livemon: Specify localhost as string

Traceback (most recent call last):
  File "/home/vasko/gr38/lib/python3.7/dist-packages/gnuradio/grc/core/FlowGraph.py", line 216, in renew_namespace
    value = eval(parameter_block.params['value'].to_code(), namespace)
  File "<string>", line 1, in <module>
NameError: name 'localhost' is not defined

Change-Id: I6bae2fb1f09038cb0cd3410533d3b3fdc79ed354

apps/grgsm_livemon.grc

@@ -179,7 +179,7 @@ blocks:
     label: IP or DNS name of collector point
     short_id: ''
     type: str
-    value: 'localhost'
+    value: '"localhost"'
   states:
     bus_sink: false
     bus_source: false

apps/grgsm_livemon_headless.grc

@@ -134,7 +134,7 @@ blocks:
     label: IP or DNS name of collector point
     short_id: ''
     type: str
-    value: 'localhost'
+    value: '"localhost"'
   states:
     bus_sink: false
     bus_source: false